Generally, self-sequencing multilamp photoflash arrays which operate from a high voltage source are not uncommon in the art. Such structures, the so-called Flip Flash of U.S. Pat. No. 3,894,226 for example, normally operate from a piezoelectric source controlled by the shutter action of a camera and provide high voltage pulses in the range of about 500 to 4000 volts. These relatively high voltage pulses are utilized in conjunction with radiant-activated switches to provide sequential activation of multilamp photoflash arrays.
One known high voltage arrangement is suggested in U.S. Pat. No. 4,182,608 issued Jan. 8, 1980. Therein, a high voltage source provides voltage pulses of a magnitude sufficient to convert a radiation switch from a high to a low resistance path. Also, the radiation switch includes a silver source, such as the suggested silver carbonate, and a metal containing material such as titanium metal and titanium hydride.
Although the above-mentioned high voltage self-sequencing structures have been and still are utilized in many popular photolamp arrays, there is a notable absence of self-sequencing structures utilizing a low voltage or battery-operated type voltage source. This conspicuous absence of low voltage self-sequencing multilamp arrays is believed to be a result of poor reliability of the self-sequencing array due to undesired variations in the resistance of the available radiant-responsive chemical-type switches available. It is believed that these undesired resistance variations which cause serious current limiting to a filament-type low voltage flashlamp have rendered flash reliability unacceptable in self-sequencing low voltage arrays.
More specifically, it is believed that the known and available radiant-activated switches leave much to be desired insofar as post-conversion electrical resistance capabilities, mechanical integrity, and adherence are concerned. Although post-conversion resistance values as high as 2-ohms or greater are of no great consequence in a high voltage self-sequencing array, such values are intolerable in a low voltage type structure. Also, excessive gas evolution, as a result of decomposition of gas-releasing species, is deleterious to the adherence capabilities of a radiation-responsive type switch. Moreover, increases in binder content in an effort to compensate for poor adherence due to gas evolution tends to undesirably increase the post-conversion resistance of the switch.